Processing errors sometimes occur during the manufacture of wafers of integrated circuits. Processing errors are a major cause of the creation of integrated circuit wafer scrap during ion implantation procedures. For example, if the wafers that are loaded into an ion implantation system have already been implanted, then subjecting the wafers to a second ion implantation process will ruin the wafers. In many ion implantation systems there is presently no way to know whether the integrated circuit wafers have been correctly loaded into the ion implantation system.
FIG. 1 illustrates a block diagram of an embodiment of an exemplary prior art system 100 for implanting ions in integrated circuit wafers. Prior art system 100 comprises an ion implantation system 110. The prior art ion implantation system 110 may comprise, for example, a GSD200E2 Ion Implanter manufactured by Axcelis Corporation. The ion implantation system 110 comprises a wafer cassette 120 that is capable of holding an integrated circuit wafer 130 during an ion implantation process.
The ion implantation system 110 also comprises an ion implantation control system 140 that controls the ion implantation process in the ion implantation system 110. Ion implantation control system 140 comprises computer hardware and software that controls the timing and intensity of the ion implantation process that implants ions in the wafer 130. As shown in FIG. 1, the ion implantation control system 140 is coupled to a station controller 150. The station controller 150 comprises computer hardware and software that controls the operation of the ion implantation system 110 through the ion implantation control system 140.
The station controller 150 is also coupled to a user interface 160. The user interface 160 provides a user with information from the station controller 150 that relates to the operation and status of the ion implantation processes that are carried out in the ion implantation system 110. The user interface 160 may comprise a computer display, and a keyboard, and a computer mouse (not shown in FIG. 1) and other similar types of conventional computer access devices.
The ion implantation system 110 comprises a sensor unit 170 that is coupled to the wafer cassette 120 and that is also coupled to the station controller 150 through the ion implantation control system 140. The sensor unit 170 receives an electronic signal from the wafer cassette 120 that indicates that a wafer 130 has been placed into the wafer cassette 120. The sensor unit 170 also sends an electronic signal to the station controller 150 that indicates that a wafer 130 has been placed into the wafer cassette 120.
When a wafer 130 of integrated circuits is placed into a wafer cassette 120 and placed into position within the ion implantation system 110, there is presently no way for a user to know if the wafer 130 is a wafer than has already been implanted. There is also no way for a user to know if the wafer 130 that has been placed into the wafer cassette 120 correctly corresponds to and matches the wafer information with which the station controller 150 identifies the wafer that is presently within the wafer cassette 120. There is presently no way for a user to be sure that the wafer 130 that has been placed into the wafer cassette 120 has been correctly identified.
A wafer 130 that has been subjected to an incorrect implantation process is ruined and has to be discarded as scrap. Incorrectly identifying wafers and subsequently incorrectly implanting those wafers is a major cause of errors in the ion implantation process. One study estimated that as many as ten or eleven wafers per week are ruined by such processing errors. The loss caused by incorrectly implanted wafers may amount to a considerable amount of money and time.
Therefore, there is a need in the art for a system and method that allows a user to reduce the number of processing errors that occur during an ion implantation procedure. There is a need in the art for a system and method that is capable of efficiently identifying a wafer that is located within an ion implantation system before an ion implantation process is carried out on the wafer.